Method of decarbonizing filaments for incandescent lamps.



IATEs Perm OFFIGE.

. zranmg GERMANY. I ammo]: or n fifmonnmo manure Ion magnu Lm To allwhom it. may Be it known that I, HnRMANN'ZEnNmo, a subject of the Kingof Prussia, and resident of Halensee, near Berlin, in the Kingdom ofPrussia, German Empire, have invented new and'useful Improvements inMethods of Decarbonizin Filaments for Incandescent Lam s, of which thefollowing is a full, clear, an exact description.

In the manufacture of the filamentsconsisting of metallic compounds forincandescent lamps, it is necessar to obtain the finished filaments asclear f iom carbon as ossible, because a small quantity of carboninfluences the resistance or stren th and usefulness of the filamentsconsiderably. Most methods hitherto contrived for this purpose cannot becarried out on a large scale without great dilficulty and scarcelypermit the perfect removal of the carbon unless means are used whichsimultaneously attack the metal of which the filament consists.

My'present invention is intended to enable the filaments to becompletely decarbonized on a large scale without the metal of thefilament suffering.

The invention consists in decarbonizing the-filament by means ofnitrogen gas or nitrogenous gases, roduced byheating phospham (PN H)with or without an addition of phosphorus in a vacuum.

The nitrogen contained in phospham passes off at a relatively lowtemperature, and forms, in a free state,.with the carbon, cyanogen orthe like, or oxidized compounds of the same. The phosphorus, 'whichbecomes free simultaneously. is able to combine with the oxygen stillpresent, or to exert its reducing action on the metal oxid impurities,which may perhaps still be present in the filament. The phosphorus addedis of special importance when it may be assumed that the. filamentcontains a considerable quantity of oxygenous impurities.

In carrying out the invention a small percentage of phospham to whichsome phosphorus may be added is mixed withthe metal powder from whichthe paste used for squirting the filaments of incandescent lamps is madeand then a paste is very carefully prepared. The amount of phosphamdepends on the nature of the binding agent used .and is larger accordingas the binding agent contains more carbon. The

v Y -Bpeeiflcgtion of Letters Patent.

Appjlgefion flied; emb ao,'19os. Serial No. 841,340,

Patented Jan. 5, 1909;

proportion of phospham in the finished paste amounts to 4 per cent., forinstance, when tar is employed as the binding agent. The action of thephospham takes place immediately, when the filament is made incandescentin a vacuum, as it then becomes absolutely free from carbon without itsstrength being impaired in any manner.

Another method for carrying out the process is designed to liberate thenitrogen contained in the phospham and to allow it to act exteriorly onthe filament. In this case the filaments are placed in a suitablefurnace, in which a vacuum is produced. The furnace is then heated up toabout 130, in order to remove the water and the products ofdecomposition evolved at that temperature, whereupon the taps of the pumare closed and the furnace is now heat slowly up to 800 to 1000 C. Thephospham is decomposed and the nascent gaseous materials will have apressure of some millimeters of mercury according to the quantity ofphospham employed. amount of phospham depends on the binding agent used1n manufacturing the paste for the filaments. If the binding agent is-very carbonaceous, then a correspondingly larger quantity of phosphammust be employed and the heating correspondingly prolonged. Filamentstreated according to this process are perfectly free from carbon and arefirm. This heating process may also be carried out with the assistanceof the electric current in any vessel in which a vacuum can be produced,or in the bulb of an incandescent lamp. When the filaments are thustreated, said filaments can bedusted over or otherwise coated withphospham. For example, finely powdered .phospham can be mixed with apaste which is applied to the filament with a brush. -When the filamentso coated is rendered incandescent by the electric current nitrogen isalso separated.

If the filament is to be decarbonized after it has been inserted in thebulb of an incandescent lam the following method is preferably empoyed:-Powdered phospham is mixed with alcohol and then applied tothefilaments before it is melted down. Instead of this, the phospham pastecan be placed on the electric wires, supports etc. exhausting the airout of the bulb by means of a pump, the tap between the lamp and theair-pump is closed and the lamp is made The After in the lamp is notlessened.

- ed 'outsi current. The phospham is thus vaporized no matter where itmay be situ the lamp. Finally, itmay be mentioned, that the phos ham mayin this casealso be heate the lamp in a' space, which may be connectedwith the lamp. Of, course the arrangement must be such that the vacuumHaving thus described my invention, what I claim as new and desire tosecure by Letters, Patent is 1.-The method of producing a decarbonizedfilament for incandescent lamps, consisting in lacing a filament in acompartment, pr

ment, and heating said filament'in said comucing a vacuum 1nsaid'compartwhile maintaining the vacuum:

7 2. The "method of producing-a decarbonwitnesses.

ERNING.

two subscribin HERMAN N Witnesses:

HENRY HASPER, Womnmnn Ham.

the presence of maps Mama's v v o I 7 -20. ized fi1amentfor incandescentlamps, conmyname this 30th day of August 1906, in i

